High – Temperature Superconductivity

High
– Temperature Superconductivity

Recently, researchers at Argonne National
Laboratory have discovered a nickel oxide compound as a material for
high-temperature superconductivity. John Mitchell led a team that synthesized
crystals of a metallic trilayer nickelate compound through a high pressure
crystal growth process. This process
combined crystal growth, x-ray spectroscopy, and computational theory to
produce the nickel oxide compound. “It’s poised for super conductivity in a way
not found in other nickel oxides,” Mitchell stated.

Superconducting materials are extremely
important technologically because electricity is able to flow through without
experiencing any resistance. At first, low-temperature super conductivity
seemed possible, but was impractical because items must be coolers to hundreds
of degrees below zero. But in 1986, high-temperature conductivity was
discovered in copper oxide compounds, cuprates, brought upon a new
technological phenomenon. A
high-temperature superconductor could potentially lead to faster and more
efficient electronic devices that can transmit powers without any sort of
energy loss, as well as levitating trains that will be able to travel on
frictionless magnets rather than rails.

For years, it hasn’t be exactly clear how
cuprate superconductivity works, so researches have been looking for
alternative solutions. Nickel-based oxides, nickelates, for a while have been a
potential cuprate substitute because of the similar properties. The journey has had their ups and downs and
very little success have been achieved, but they are slowly but surely making
progress.

The team was able to create a
quasi-two-dimensional trilayer compound. This trilayer consists of three
separate layers of nickel oxide that are separated by spacer layers of
praseodymium oxide. Mitchell described the nickel looking more two-dimensional
rather than three-dimensional, both structurally and electronically. The
nickelate as well as a compound that contains lanthanum rather than
praseodymium both share a quasi-two-dimensional trilayer structure. The
lanthanum component is non-metallic but adopts a “charge stripe” phase, which
is an electronic property that can help act as an insulator. This insulator
like material is the opposite of a superconductor. The praseodymium system is not capable of
forming the similar stripes, but remains metallic and is the more likely
candidate for superconductivity.

The Argonne Laboratory is one of the very
few places in the world that is capable of creating the compound. There are
special capabilities that the high-pressure optical-image floating zone furnace
is able to do to allow the crystals to grow properly. By taking X-ray
absorption spectroscopy and performing density functional theory calculations,
the electronic structure of the compound is similar to cuprate materials.

This is just first few steps of
discovering, and the team will be attempting way to help induce the
conductivity.